Oscillator-amplifier radio circuits



Feb. s, 1949. J J. ANTALEK 2,461,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS Filed May 31, 1943 5 Sheets-Sheet 1OUTPUT AF OUTPUT INVENTOR.

fa/up .IAnZaZek ATTORNEY Feb. 8, 1949. J. J. ANTALEK 2,461,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS Filed May 31', 1945 4 5 Sheets-Sheet2 IN V EN TOR. JZFMLJAZZ Z'aZeir Feb. 8, 1949. J. J. ANTALEK 2,451,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS Filed May 31, 1943 5 Shets-Sheet sIN VEN TOR. Jofimf Feb. 8, 1949. J. J. ANTALEK OSCILLATOR-AMPLIFIERRADIO CIRCUITS 5 Sheets-Sheet 4 Filed May 31, 1943 INVENTOR.JomJ'AnZ'aZek BY fl 44M 0L Feb. 8, 1949. J. J. ANTALEK 2,461,306

OSCILLATOR-AMPLIFIER RADIO CIRCUITS 7 Filed May 31, 1943 5 Sheets-Sheet5 Patented Feb. 8, 1949 QSCILLATOR-AMPLIFIER RADIO CIRCUITS John J.Antalek, Chicago, 111., assignor to The ticn of'Illinois RaulandCorporation, Chicago, 111., a corpora- Application May 31, 1943, SerialNo. 489,235-

7 Claims.

This invention relates to electronic tubes and the. circuits connectedthereto, especially relating to. devicesemployed. in. connection withradio reception. and. transmission.

One purpose ofthis inventionis to provide circuits utilizing. a single.electronic tube, in which circuits such tube will perform a plurality offunctions, such as the functions which hitherto harerequired the .use ofmore than one electronic tube;

Another purpose of this invention-is to provide aI-radio telegraph or,telephone receiver in which the total number of electronic tubesrequired is reduced below that. hitherto found. necessary, more:particularly in. connection with radio receivers of the. superheterodynetype.

Still another purpose of this invention. is to providea radio receiverin. which an. electronic tube normally functioning to cooperate with theremainder of the receiver for the purposes of signalreception,willlikewise. function as a source of electrical oscillations ofpredetermined frequency; which oscillations may be utilized to calibratethe receiver as a whole.

A still. further. purpose of this. invention is to provide. a circuit inwhich a single electronic tube functions simultaneously as an audiofrequency amplifier and as a radio frequency oscillator.

Yet another purpose of this invention is to provide a. radio receivingcircuit in which an electronic tube-functioning as an audio frequencyamplifier, obtains its grid bias voltage by simultaneously functioning.as anos-cillator at a superaudible frequency, the superaudibleoscillations giving rise to thebias required by the tube as an audiofrequency amplifier.

Another purpose of this. invention is to. provide a radio receivingdevice inwhich av single electronic. tube performs thesimultaneousfunctionsof auoscillator producing a beat note with an incoming signal,of: a. diode type, detector of such. signal, and of anaudio amplifier ofthe signal, after detection.

A; still' further object. of this invention is to provide, in asuperheterodyne radio receiver, a circuit in. which a single electronictube functions simultaneously as anv amplifier of intermediaterequencies and of audio frequencies, thereby allowing the eliminationofat least one electronic tube hitherto employed to fulfill only one ofthese functions.

' A yet further object of this inventionis tov provide aradiotransmittingcircuit inwhich. a single electronic: tubefunction-s. bothas. an oscillator,

' 2 with or Without crystal'control, and as a speech amplifying tube.

Still further objects and. advantages of this invention will be apparentto those skilled in the art, among which advantages are those of economyof material, space and weight, in radio telegraph or telephonetransmitters and receivers. Such advantages are. of particularimportance in connection with portable radio transmitting and receivingequipment,

Reference is now made to the accompanying drawings, where Fig. 1 is aschematic diagram showing a portion of a complete circuit, according tothis invention, wherein a single electronic tube of the multi-elementtype, performs the function of a detector, an audio frequency amplifierand a crystal controlled oscillator.

Fig. 2A is a. schematic representation of a portion of a circuit whereina single triode is used simultaneously as a high frequency oscillatorand as an audio-frequency amplifier.

Fig. 2B is a schematic drawing of a portion. of a circuit, utilizing asingle tetrode to accomplish the same results given by the triode ofFig. 2A.

Fig. 3A is a schematic representation of a portion of the circuit of aradio receiver of the superheterodyne type, illustrating the use,according to this invention, of a single electronic tube of themulti-element type as an amplifier of received signals at anintermediate frequency, as a detector of suchamplified signals, andlikewise, as an amplifier at audio frequency ofthe thus detectedsignals.

Fig. 3B is a schematic showing of amodified form of the circuit of Fig.3A.

Fig. 4A isaschematic showing. of aportion. of a circuit wherein a singletetrode is simultaneously used, according to this invention, as anaudiofrequency amplifier and. as a. crystal controlled oscillator.

Fig. 4B is a schematic showing of a modification of the circuit, of Fig.4A, in which a variable frequency oscillator circuit is substituted forthe crystal controlled oscillator circuit of Fig. 4A.

Fig. 5 is a schematic showing of a radio telephone transmitter embodyingcertain principles of this invention, including a crystal controlledoscillator circuit.

Fig. 6 shows schematically a modified form of a portion of the circuitof Fig. 5, employing an oscillator circuit wherein. the frequency isdetermined by the electrical constants. of a coil and a condenser. inlieu of. the crystalcontrol shown in.v Fig. 5.

Fig. 7 shows a circuit using a single tube as a beat frequencyoscillator, a detector and an audio amplifier.

Referring now to Fig. 1, there is here shown the portion of asuperheterodyne receiver immediately following the portion thereof whereamplification has been accomplished at an intermediate frequency. Theinput transformer shown at I may conveniently have its primary I0! tunedby condenser I02 to the intermediate frequency employed by the receiver,while the secondary I03 is similarly tuned by condenser I04, to the samefrequency The intermediate frequency is applied through lead I05 to thediode plates I05, I06 of electronic tube I07. The intermediate frequencyreturn to ground is made through by-pass condenser I08, and cathode I09of tube I0! is likewise grounded. Resistor H0 acts as a filter resistorfor the intermediate frequency, in connection with by-pass condenserII'I, connected to the ground at one side. Resistor H2 is likewiseshunted to ground across condenser III and constitutes a potentiometertype volume control by virtue of the variable connection point I I3through which the rectified and filtered audio frequencies are takenoff, via audio grid coupling condenser Iii, and applied through radiofrequency filter resistor H5 to control grid IIG of tube I01. Thepotential of grid II6 is maintained via grid leak resistor I I1,connected from the lower end of resistor H5 to the ground.

The amplified audio frequency output of tube IE1 is taken off from theanode H8 thereof and supplied to the audio frequency output terminalsH9, H9, via audio frequency coupling condenser I and from groundconnection I2I. The D. C. operating energy for anode H0 may be derivedfrom any suitable source such as that indicated at I22, via anode loadresistor I23, the anode like wise being connected to ground throughradio frequency by-pass condenser I23.

The screen grid I24 of tube I01, is kept at a suitable D, C. potentialby connection to the source indicated at I22, via voltage droppingresistor 525, beingeffectively maintained at ground potential, withrespect to A. C., by means of audio frequency by-pass condenser I26.Likewise interposed between by-pass condenser I26 and screen grid $124,is inductance I 27, of which a portion may be shunted out by means ofswitch I28. Shunt connection I29 also is extended from screen grid I24,via output coupling condenser 30. This shunt output connection serves asa means whereby the oscillatory energy developed, as hereinafterexplained, by tube I0'Lmay be applied to another desired purpose, forexample to the input of a radio frequency tube located at a prior pointof the receiving circuitl The operation of tube I01 as an oscillator, isbrought about as a connection of a piezo-electric crystal ISI betweencontrol grid I56 and ground point I32. Inductance, I21 should be sodesigned that its resonant frequency, when connected as shown, willmatch that as shown of piezo-electrio crystal I3I, or some harmonicthereof. The closure of switch I28 will destroy such resonantrelationship, and thereby will cause tube I01 to cease functioning as anoscillator, if so desired.

The output of tube I07 functioning as an oscillator may be used forseveral purposes. If connected as above-described, to an earlier portionof the receiver, or as indicated by dotted line I40, to the primary ofthe last intermediate frequency tube of the receiver, it may be employedas a dii producer of the beat frequency used in the intermediatefrequency amplifier stages of the receiver. Alternatively, the variousharmonics of crystal I3I may be fed back into the receiver and employedas calibration frequencies therefor.

Still another mode of employment of the circuit of Fig. l, contemplatesthat the crystal oscillator controlled section of tube ill? shall bearranged to deliver an oscillatory output at a frequency approximatingthat employed in the intermediate stages of the receiver, so that anaudio frequency beat note may be produced by suitable combination ofthese two frequencies, thus enabling audio frequency reception ofunmodulated continuous wave signals. For this last mentionedapplication, it may be found expeditious to substitute for the crystalcontrol of frequency, an oscillatory circuit employing actual physicalinductance and capacity, as will be understood by those skilled in theart.

Making reference now to Fig. 2A, the electronic tube 200 has its controlgrid 20I connected via radio frequency choke coil 202, to the secondarywinding 203 of audio frequency input transformer 204, primary winding205, of this transformer, being supplied with the audio frequency inputsignals. Audio frequency by-pass condenser 206 is connected to theground and constitutes a portion of the return path for the audiofrequency signals to the cathode 201 of tube 200. The static potentialof control grid 20I is maintained by grid leak resistor 208, alsoconnected to the ground.

The audiofrequency output of tube 200 is conveyed from the anode 209thereof, to primary winding 2 I0 of output transformer 2 I I, the audiofrequency output of the entire amplifier being drawn from secondarywinding 2I2 of transformer 2. Radio frequency by-pass condenser H3 isconnected directly from anode 209 to the ground and functions to preventthe development of unwanted radio frequency across winding 2I0, theorigin of such pot n-tials being hereinafter explained.

The cathode 20'! oftube 200 is connected to an intermediate point ofinductance 2M, this inductance functioning to determine production ofoscillations by tube 200. The lower end of inductance 2I4 is grounded,and the upper end thereof is connected to control grid 201 viaoscillator grid condenser 2I5. It will be apparent to those skilled inthe art that this mode of connecting the grid, anode and cathode,respectively, of tube 200, to inductance 2 I4, constitutes a wellknowntype of oscillatory circuit employed in connection with electronictubes.

When tube 200 is set into oscillation by reason of the oscillatorycircuit connection just described, there will be developed acrossresistor 208, a D. C. potential which will serve to maintain controlgrid 20I at a suitable D. C. potential, for the proper functioning oftube 200 as an audio frequency amplifier. The reason for the presence ofradio frequency by-pass condenser 2I3 will now fully be apparent.

In Fig. 2B the audio frequency input through grid coupling condenser 250to control grid 25I of tetrode 252, via radio frequency filter resistor253. Control grid 25I is likewise connected to ground via grid leakresistor 254. Anode 255 of tube 252 is likewise grounded with respect toradio frequency, by means of by-pass condenser 256 and derives itsoperating energy from any suitable source, such as that indicated at 3+,via primary winding 257 of audio frewith the anode circuit Of tube 3iquency output transformer 258, from "the secondary -winding2'59 of whichis "delivered suc'h audio frequency output. A voltagedroppingresistor"266 is connected rbetween the source of energy just described and the*screen ;grid 261 of tube 252, this screen grid being by-matssed toground by condenser 262. r

The oscillatory function of tube "252 is- 'brought aboutby'the'connectio-n of the cathode 263thereof to -an intermediate pointon inductance 264, this inductance being grounded at its "lower 'end andconnected at its upper end via oscillator grid condenser '265 to control'grid 251 of the tube. Since the-dual='functioning of tetro'de 252 andthe maintenance of control grid 25lat the proper operative "D. C.potential by means of resistor 25s, are brought aboutinthesame-Tashion-as alreadydescribed'in connection with Fig. 2A,adetailed recitation thereof is thought unnecessary.

Referring now to Fig. 8A, th, signal-bearing currents receivedat'antenna 353i) and ground'ttl pass through the primarywinding 3832 ofthe-antenna coupling transformer t3, the secondary winding 304 of whichtransformer is suitably tuned by variable condenser '395. One end ofsecondary 335 is connected 'to control grid 386 of mixer or convertertube 387, while-the other endof secondary 3M-is grounded via by nasscondenser'SBB. Resistor Still alior'ds a bias ior'grid *lations. "Theoutput of mixertubeBllI is taken from the anode 3W "thereoigandtransformer 3 l 8 has the primary windings l t connected in series This'primary winding is tuned'to a 'suitabl'eintermediate frequencyequivalent to the' beat frequency produced by tube 3%! and itsassociated circuits/by -means-o'f condenser "320. The anode supplycircuit extends from the lower portion of trans- 'former Sta tothepointin'dicated by 13+, indicating any suitable source-ofD.Cfhigh-potential. 'The'remaininggrids fiM and 322 of tube 301 mayconveniently obtaiirth'eir voltage supplyfrom the same source whichieeds the anodeofthe tube, via a voltage dropping resistor e23, beingsuitably by-passed tmground :via condenser 32%.

'The intermediate frequency'signal bearing energy derived from tube 38'!and the associated circuits just described, will then :appearinsesondary :winding 325 of l-Ftransfo-rmer M8, this last winding :beingrlilrewise-tuned by condenser J3Zfift0 a'frequency; correspondingtoithat to which the primary windingoftransformert8 is tuned.Secoridarywvinding 325 is. connected at one end to control gridi-32l ofamulti-element tube 132%, 'and isrconnectedrat theother end'to'gmund via"IF by epass condenser-1:32 9. Tube vr323 'hasathe cath- =odesilflsgroundediand thcscreen gridcfifil thereoi-niay receive its energyfrom' 'theicommonzsupcply indicated at 3+, through :a suitable voltage:dropping resistor Q32 andri-s by-passed {to ground shy-[condenseri'EtheiIFsignals fed-tozgridruzl will be amplified "by tube 328 and theamplified signals appearingon the-anode 33:3 of this tube are fed intoprimary winding 335 of a second intermediate frequency transformer3.5-3.6, this primary being tuned by condenser 33? to the frequency ofsuch :Il'? signals and being Icy-passed to ground via condenser 33?.Secondary Winding 3380i transformertsii islikewisetuned by con--denser-339 andfeedseleinent 1M3 oi tubetfis, this tube-elementfunctioning to afford diode detector action. The low frequency signalsresulting from suchidetecting action app-ear acrossload resistor 13%,the usual smoothing or intermediate frequeue-y by pass condenser 6&2 andIF filter resisttor 3 3i being connected from the lower end of winding338 M the ground, the path for resistort li being vie/load resistor 3%.

The audio frequency signals which have resulted from the IFamplification and detection 'just described will then feed back viaconductor 3 32 to the lower end of secondary Winding 325 of transformerDue to the relatively low impedance presented byt-his winding" to audiofrequency currents, such signals appear, practically 'unreduoed inintensity, upon control grid '32? of tube 323. In .tl'iismanner, theamplifier section of tube 328 :willperformthe additional function or"amplifyingthe audio frequency currents fed :into grid 1321, While at thesame time it is ampli- :iying the'IF currents, as previously described;

The amplifiedv audio-output of tube appears w-across the anode loadresistor it-3. it will be :noted that the lay-passing action orcondenser 33'! allows the intermediate frequency signals fed to primarywinding 335 of transformer 33%, to

pass directly to ground without being weakened by :passage through theresistor just described. From the junction point between the upperend-ofresistor 343, which resistor likewise servesrto'supply anodepotential to tube 328, and the lower end of primarywinding-335, istaken-a ead 3 3d, through which the ultimate amplified audio-frequencyoutputbi tube passes, via audio frequency coupling condenser "3 5 and isfed to volume control i345, :oi the potentiometer type, ultimatelyreaching ground through conductor. 341.

'Atit irt, is shown an output or 'power amplifier tube whichperformsonly the single iunction'of 'handlingthe audio frequency signals fed tothe 'gri'dfd thereof-from Volume control'fi lb. Tube :tfiilzhas the gridbias suitably determined by cathode resistoriii'il, by pass condenser355 connectediin shunt therewith Screen grid liil and anode 353 of tube:3- l 8,-may conveniently receivetheir potential from a common sourceindirouted at 13+. The audio frequencyoutput of tube :tdil'is fed to theprimarywinding 35 of output transiornrerisdt, from, the secondarywinding 3156 113i which such audio frequency-output maybe atalren.

Inzthe recei-ver just describedthe plural functioning oirtube allows theeliminaticn ofthe intermediate frequencyainplifier tube which has'ihithertobeen found necessary, thus allowing the receiver to "be-builtwith greater economy of ma- :teriaLspac-eandweight.

Referring now to Fig.3B, the antenna circuit 'andtheunixer tubecircuits, including the input circuit to tube "328, are shownrespectively as identical with the like portions of Fig. 3A and :bearidentical reference numerals. The diode element ten :of tube 328likewise is fed from an intermediate frequency transformer see, havingaytuned secondary -:circuit x338, .339, in :the same fashion asindicated in Fig. 3A. This secondary circuit is by-passed forintermediate frequency to ground by condenser 342, and an intermediatefrequency filter resistor 341 is placed in series with the diode loadresistor 390, the audio frequency output appearing across resistor 380The tuned primary circuit 335, 33?, of this transformer is placed inseries with the circuit of screen grid 331 of the tube, instead of beingplaced in series with the anode 335 thereof. Voltage dropping resistor332 is connected between the lower end of this tuned primary circuit andthe source of high voltage which feeds the anode circuit of tube 328.but by-pass resistor 333, connected directly between the lower end ofthe tuned primary circuit and the ground, serves to prevent loss ofintermediate frequency energy in resistor The audio frequency outputfrom the anode circuit of tube 328 appears across plate load resistor343, which, in this case, is directly coupled at its upper end to anode334 and Icy-passed with respect to intermediate frequencies, directly toground by condenser 33?. The lower end of resistor 353 is connecteddirectly to the source of anode potential by means of conductor 34 3'.The amplifier audio frequency output of tube 328 is delivered throughstopping condenser 345 and may be withdrawn between the open side ofthis condenser and the ground as indicated in Fig. 318 by the legend "AFoutput. In Fig. 3B the final output tube corresponding to tube 058 ofFig. 3A, is omitted, since its function is identical with that indicatedin Fig. 3A.

The placing of transformer 350, feeding intermediate frequency energy tothe diode portion of tube 320, causes this tube to function as a triodeamplifier of intermediate frequency energy, while the fact that theaudio frequency output is drawn from anode 334, causes the tube tofunction as a tetrode, with respect to the audio frequencyamplification. This mode of connection results in less gain at theintermediate frequency. However, the oscillation of the anode loadcircuit from the intermediate frequenc circuits connected to this tube,allows the use of a larger size anode load resistor as element 343, thusrendering possible a greater audio frequency amplification, withoutcausing any reduction of the intermediate frequency gain. In practice ithas been found that the overall gain of the circuit indicated in BB issomewhat less than that of the circuit indicated in BA, but theisolation of the audio frequency output has been found desirable incertain applications.

Referring now to Fig. 4A, tube 400 has connected between control grid401 and anode 492, a crystal 503, which causes the tube to functionaccording to the type of the so-called Pierce oscillator. At the sametime the tube receives an audio frequency input from terminals 404,through coupling condenser 405 and resistor 406, the grid 451 beingmaintained at a suitable potential by means of a grid leak 40?. Theanode 402 is isolated by radio frequency choke coil 008, but the audiofrequency output passes through this choke coil and appears across theprimary 409 of output transformer 519, available across the secondarywinding 411 of this transformer. A suitable source of anode energy isindicated at 13+ and this same source may conveniently be fed throughvoltage dropping resistor 412, to screen grid 413 of the tube, asuitable by-pass condenser 414 being provided.

In Fig. 4B is shown tube 400 with a similar audio frequency feedcircuit, as indicated by like reference numerals. In this case, theradio frequency oscillation of the tube is brought about by connectingthe cathode 450 to a suitable intermediate point 451 of inductance 452,the upper side of this'inductance being coupled by oscillation condenser453 to grid 401, while the lower end of the inductance is grounded at454.

A variable condenser 455 is shunted across coil 452 and serves todetermine the frequency of oscillation of the circuit. In this case,there is indicated a resistance coupled output circuit from anode 402 ofthe tube, including by-pass condenser 450, load resistor 45?, andcoupling condenser 458, the audio frequency output being availablebetween the free side of condenser .558 and the ground, as indicated onthe drawing.

The combination audio frequency amplifier and radio frequencyoscillators, as shown in Figs. iA or 43 may have their radio frequencyoutput utilized for any convenient purpose, such as to feed a mixertube, as a beat frequency oscillator, and so forth, as previouslymentioned in connection with the circuit of Fig. 1.

In Fig. 5 is indicated a radio telephone transmitter, where microphone5130 serves to modulate energy received from battery 501 and is coupledvia input transformer 502 and radio frequency choke coil 503, to thegrid 504 of tube 505. A crystal 506 is connected between grid 504 andthe ground while the return D. C. path of the grid is completed throughbiasing resistor 50'', shunted by by-pass condenser 508. The operationof this biasing resistor, when tube 505 is in oscillation at a frequencydetermined by crystal 506, is similar to that already described inconnection with Fig. 2A, the higher frequency oscillations thus creatinga suitable D. C. bias for tube 505.

The screen grid 50?: of the tube is employed as an anode, and variablecapacity 5m, shunted across inductance 5i 1, constitutes the oscillatorytank circuit, tuned to the frequency of crystal 505. This constitutes atuned grid-tuned plate oscillator, the output of which is coupled viagrid coupling condenser 512, to power amplifier tube 513, the grid 514of this tube being maintained at a suitable potential by grid leakresistor 515. Tube 513 is anode modulated by the audio frequency outputderived from the anode 516 I of tube 505, this anode being suitablyby-passed with respect to radio frequency by means of condenser 517,while the audio frequency output thereof is impressed via modulationtransformer 518, and the anode tank coil 519, connected to the anode 525of the power amplifier tube 513, this anode tank coil being tuned byvariable condenser 521 to the frequency of crystal 505. A suitable radiofrequency by-pass condenser 522 shunts the'the secondary winding oftransformer 518.

The voltage dropping resistors, by-pass condensers and high voltageconnections of the screen grids of tubes 505 and 513 are indicated inconventional fashion, and a detailed description thereof is thought tobe unnecessary. A complete radio telephone transmitter is thus obtained,with the employment of only two electronic tubes.

Referring now to Fig. 6, there is here indicated an alternativearrangement of tube 505, in which a self-excited oscillator circuittakes the place of the crystal 506 cf Fig. 5. The input transformer 502,is connected to control grid 504 via the lower portion of a splitinductance 600, indicated by the dotted lines in Fig. 6. The upper '9portion of inductance-800 is introduced in series with the circuitconnected to the screen grid'56-9 of tube50'5, and is tuned by condenserfifll, thus constituting the tuned tank circuit'determining the radiofrequency period ofthe circuit. A suitable radio frequency by pa'sscondenser 602 is connected from the upper end of the-secondary oftransformer -592 to the ground, thus affording a-direct path for theradio frequency currents circulating through the lower portion of splitinductance 600.

The radio frequency grid coupling condenser 5 l-2,-by-pass condenser 5l1and modulation trans former 518 are connected in the same fashion asshown in Fig. 5 and it is thought unnecessary again to indicate theradio frequency power amplifier tube and antenna'connections, sincethese 5 may be made idential with those shown inFi xd Making referencenow to Fig. 7,'=there ish'ere shown a portion of'a superheterodyn'etype'radio receiver, including the last'stage of intermediate frequencyamplification, together with the input and output coupling devicestherefor. Likewise there is shown in this figure amulti-element-lectronic tube connected both to the input and the outputof this final stage of intermediate frequency amplification. Thislast-mentioned tube functions simultaneously as an oscillator, pro-'ducing current of a frequency which'will beat with the intermediatefrequency, as a diode typedetector and as a high gain'audio frequencyamplifier.

Tube 190 is shownas of the tetrode'type;butit is understood that thistube may be-of-any 'other type suitable for intermediate frequency amplification, for example a pentode, and-changes in the circuit here shown,in order to adapt it for the use of such other type tube, will beapparent to those skilled in the art. Cathode m of tube 100 is kept at asuitable operating potential by means of bias resistor 102, by-passed bycondenser !03. Heater lil imay be fed with energy from any. suitablesource (not shown). The control grid 105 is kept at apotentialdependentupon the potential of conductor H15, as feed throughfilter resistors 70"! and 108. The use of such variable potential inorderto secure automatic volume control is well known in the artand adetailed description thereof isltherefor'e thought to be unnecessary.Input transformer 1'08 =is shown with a primary winding 109, suitablytuned by a capacity I i ll, while secondary winding ll is likewise tunedby capacity H2. The output of transformer 103 .is .fed between controlgrid T05 and the ground, the latter connection being made viaintermediate frequency by-pass condenser H3. Screen grid H4 is fed froma suitable high potential source indicated at H5 by the legend B+,through voltage dropping resistor H6 and is by-passed to ground bycondenser H1.

The amplified output of tube is taken from the anode 1 l 8 thereof andfed to primary winding H9, suitably tuned by condenser 120, ofintermediate frequency output transformer 'l2l. Secondary winding I22,of transformer 12l, also suitably tuned by capacity 123, is connectedbetween the detector element 124 of multi-elcment tube 125, and theground, the latter connection being made via intermediate frequencyby-pass condenser I26. The rectified output of the detector portion oftube 125 passes through diode filter resistor '121,by-passed to groundby another intermediate frequency condenser I28, and to resistor 129.This last resistor 129 is connected at its lower extremity to the groundand may resist 1 0 c'onvenicntl y be provided with a movable contact130, functioning as a volume control, "and feeding audio frequencyenergy through boupling con denser 13 lfto the audio frequency amplifiersection input-of tube T25.

Tube F2 5 has the cathode 32 thereof grounded vand cathodelheater 133may be-fedi'from imys'uitable sourceof'e'n'ergy (not shown). The audio 7frequency input for tub'e' Tl 2 5, obtained via *aud-i'o fr'equencycouplingcondenser 73 i is fed throu h radio frequency isolating resistor134, tocontrol grid 135, the potential Of this control gridbihgmaintained at a suitable value via grid leak resistor 133i,-'cqnr-icc'ted from the lower end of resi's tor 133' to the ground.

The amplified audi'o frequency output of tube 3 2% is taken from theanode 13! thereof, a-hd appears across output terminals 13 3, asiridihated by the-legend appended thereto. Anode 131 is fed from-'anysuitable source of energy, as indicated at 'l iiii' by th'e' legend l3+,through-plate load resistor 1 4i]. Any radio frequency components of thecurrent taken fromanodel-tl are *by passed to ground by asuitablecondenser-Hi.

The oscillation generating action of tube is brought about bet-weencontrol grid and screen grid "142. Apreferably variable inductance i 33,tune'd'bya shunt-capacity T44 to the intermediate frequency, or to somesubharlnonic thereof, is connected --directly to'ascreen grid 1 E2 and-via coupling condenser 14?: to control =grid we. "The supply-cf energyfor screen grid 1 22 may -'conveniently be obtained from the same sourceas "thesuppl'y for the anode thereof, as indicated at 146, via voltagedropping resistor WM, 'by passed to ground with respect both to radioand audio frequencies by condenser 158-. The direct current voltageapplied Via resistor '"F fl is--connected to an intermediate point 1-43upon inductance W3. A switch fill, grounded at "one side; servesoptionally to connect sc'reen; grid 1 42 to ground; via-a relativelyhigh capacity condenser 15L Whenswitch fill is closed, theconnectionofxscreen grid 152% groundserves'eifec- 'tively ztoshort-circuit a portion of i n'ductance "T43, in as far as intermediatefrequency oscillations-are concerned. Therefore, the M this switchserves to "prevent the pr od'u sucho'scillations b'y tub'e' 12%, while'at the ame time allowing the l other functions of this tube to continueuninterruptedly. I

The intermediate fre'quen'cy' Y energy appearing atthe upper end of'inductance we is transmitted 'viaconductor voltage 'coupling condenser753, to the upper end of secondary wind ing H! of transformer I08, asshown by the connection at point "154. The intermediate frequency, theperiod of which is determined by the constants of inductance M3 andcapacity 14,

is suitably adjusted, as by the variation of'the value of inductance143, so as to be sufficiently different from that of the intermediatefrequency due to an incoming signal and appearing at winding H i, sothat a beat note, usually of an audio repeat in detail such otherfunctions performed by tube 125.

What is claimed is:

1. In a combination amplifier and oscillator, an electronic tube havingcathode, control grid and anode, circuit means oscillating at afrequency range outside the audio frequency range, said circuit meanscomprising an inductance connected at the ends thereof between controlgrid and anode, and connected at an intermediate point to the cathode,means for feeding audio frequency energy to said control grid, means forwithdrawing audio frequency energy from the anode, grid biasing meanscomprising a resistor connected between said grid and ground, and acapacity bypassing said resistor for said audio frequency energy, andestablishing across said resistor a bias potential.

2. In combination, a tetrode having a cathode, control grid, screen gridand anode, an inductance connected at the ends thereof between controlgrid and anode and tapped at an intermediate point to the cathode, acoupling condenser and filter resistor in series with said control grid,means for feeding audio frequency energy to the free end of saidcoupling condenser, means for withdrawing audio frequency energy fromsaid anode and a grid biasing resistor connected between the commonpoint of said coupling condenser and said filter resistor and ground, toproduce oscillations outside of the audio frequency range andestablishing a potential across said grid biasing resistor, oscillationsbeing filtered out by said filter resistor from the audio frequencyenergy feeding means. 7

3. A device according to claim 1, in whichthe audio energy feeding meanscomprise a first transformer and the audio energy withdrawing meanscomprises a second transformer and also including a condensereffectively in shunt with the primary of said second transformer, so asto bypass said primary as to oscillatory energy.

4. In a combined oscillator and amplifier, a multi-element electronictube having cathode, control grid and anode, means for feeding audiofrequency energy to said control grid, means for withdrawing amplifiedaudio frequency ener y fromsaid anode, circuit means oscillating at afrequency range outside the audio frequency range and connected to saidcontrol grid and said anode to bias said grid, and filter meansconnected respectively to said control grid and said anode, wherebyoscillatory energy is substantially prevented from reaching said audiofre- 12 quency feeding and withdrawing means, and means for energizingsaid tube.

5. A device according to claim 4 in which said circuit means comprise atuned tank circuitconnected at the end thereof effectively between saidcontrol grid and said anode and connected at an intermediate point tosaid cathode.

6. In combination, an electronic tube including input and outputelectrodes, circuit means for feeding audio frequency energy to an inputelectrode, circuit means for withdrawing amplified audio frequencyenergy from an output electrode, means for biasing said input electrode,said biasing means including circuit means connected thereto andoscillating at a super-audible frequency, and a biasing resistor alsoconnected thereto, and filter means interposed between input electrodeand audio frequency feeding circuit means and between output electrodeand audio frequency withdrawing circuit means, respectively, said filtermeans passing said audio frequency, whereby said tube functionssimultaneously as an oscillator and as an audio frequency amplifier.

7. In combination, an electronic tube having cathode, control grid andanode, and means for energizing said tube, oscillating circuit meanscomprising an inductance connected from control grid to anode and tappedto the cathode, audio frequency feeding means connected to said controlgrid, audio frequency output means connected to said anode, a grid biasresistor connected between said control grid and ground, and meanssubstantially isolating said resistor from the oscillating currents,whereby the action of said oscillating circuit means upon said controlgrid establishes a direct current potential drop across said grid biasresistor and thereby biases said tube as an audio frequency amplifier.

JOHN J. ANTALEK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,896,268 Willoughby Feb. '7,1933 2,023,780 Cottet Dec. 10, 1935 2,059,587 Klotz et a1 Nov. 3, 19362,066,333 C-aruthers Jan. 5, 1937 2,165,764 Pitsch July 11, 19392,285,372 Strutt et al. June 2, 1942 2,293,151 Linder Aug. 18, 1942

